Hierarchies of basic goods and sins according to Aquinas’ natural law theory

Abstract

Aquinas’ natural law theory contains a set of basic goods, such as survival, reproduction and the pursuit of truth. However, whether and how there is a hierarchical relationship among these goods remains disputed. Given the importance of Aquinas’ natural law theory for Christianity and the philosophy of law, this issue merits a closer investigation. By carefully examining various modern scholars’ theories and Aquinas’ texts, it is demonstrated that according to Aquinas, firstly, there are hierarchies of basic goods and sins; secondly, these hierarchies are horizontal and vertical according to the order of participation and the dignity of substances, respectively.

Contribution: This research reconsiders the modern debate over Aquinas’ hierarchical theory of basic goods and provides a more authentic understanding of Aquinas’ own view, which can be applied to his theory of sin. Aquinas’ natural law theory can hence be clarified in a more profound way.

Introduction

Aquinas’ natural law theory contains several basic goods and sins with different severities. However, the relationship among these various basic goods is an issue that scholars have long debated in the field of natural law theory. How Aquinas designates sins with their respective severities remains uncertain as well.

Thus, this article uses a literature review and close reading to render horizontal and vertical hierarchy structures for both basic goods and sins according to Aquinas’ texts. After examining the salient ongoing debates and Aquinas’ texts regarding the relationship of basic goods, it is shown that Aquinas’ dual hierarchies of basic goods and sins are constituted with the same ontological principles. This universal framework for basic goods and sins helps one better understand Aquinas’ natural law theory.

Hierarchy of basic goods according to Aquinas and its challenges

In Summa Theologica, Aquinas (I–II, q. 94, a. 2 c., Aquinas 2007 :1009) points out that human beings have three essential, definitive elements. The most basic one is ‘being’, whose essential action is to ‘to be’, that is, to preserve life. Its higher-level definitive element is the reproduction of the human species according to its genus as an animal. That is, for an animal, the completeness of its existence lies not only in preserving its own existence but also in its own reproduction. In terms of their species, human beings, whose species is differentiated by being ‘rational’, the fundamental mode of existence is the activity of theoretical rationality (knowledge) and the activity of practical rationality (living in society). Based on these essential elements, Aquinas further deduces that human beings have three basic tendencies: self-preservation, species survival and development and knowledge, as well as participation in political life. These fulfilling activities, as objects that can be desired and are in line with human nature as ends, are the basic goods of human beings. Since good (bonum) is being (ens) with an end (finis), the two terms are interchangeable (convertibilis); thus, moral good and evil are the results of man’s free choice of appropriate ends (Te Velde 1999 :95).

Here, Aquinas clearly asserts a hierarchical sequence of human essence. Germain Grisez believes that the root of this hierarchical structure, revealed by essentialism, is its afterlife teleology, that is, Aquinas’ beatitude theory. The supreme goal of man is the vision of God (visio Dei) in the afterlife; basic goods, therefore, serve only the attainment of this final, complete good. Grisez names this attitude ‘otherworld attitude’, whereby all the goods of this world are ‘instrumentalised’ to serve the religious purpose and lose their intrinsic value. Since each good is not independent and self-sufficient but depends on the ultimate and highest good, a hierarchy of goodness arises, which is essentially a structure of dependency on goodness (Grisez 1983 :17, 25).

One of the most significant developments of Grisez’s thought is John Finnis’s list of seven basic human goods: life, knowledge, play, aesthetic experience, sociability–friendship, practical reasonableness and religion (Finnis 2011 :86–90). To Finnis, these fundamental goods are all equally important and fundamental: ‘each is fundamental’ and ‘none is more fundamental than any of the others’ (Finnis 2011 :93). Hence, the hierarchical relationship of the basic goods is subjective – whatever the good the subject most ‘focuses on’ has priority for him or her, entailing that there is no objective hierarchy among basic goods (Finnis 2011 :92). That is, although various fundamental goods still depend on each other in an instrumental way, this structure of dependency is not unchangeable and objective but optional and subjective. Thus, while one can still pursue the afterlife purpose as the ultimate end, it is no longer necessarily the highest good. The price of this is the abandonment of an objective, even ‘innate’ hierarchical order; nonetheless, the abandonment fosters human autonomy.

Double structure of the hierarchy of basic goods

How the incommensurability of basic goods according to Grisez’s and Finnis’s new natural law theory deviates from Aquinas original thought is elucidated by many scholars. For instance, S. A. Long points out that for Aquinas, the hierarchy of natural ends is morally significant prior to any subjective choice and that Finnis omits the teleological context that defines and saturates Aquinas’ natural law doctrine (Long 2001 :278–280). However, if one desires an objective hierarchical order while avoiding fundamental goods objectively reduced to instruments of afterlife goods, a possible alternative is to recognise that there is an objective hierarchy, but only one that lacks an instrumental structure.

A. L. White holds this view in his paper, where he explains how these goods can connect to form a hierarchy if they are not connected in an instrumental way.

White’s explanation relates to the relationship between the various basic goods and ‘truthfulness’. The true basic good is truly ‘universal’. The true self-love comprises the actions taken after considering the whole life of oneself, that is, not only the friendship of oneself but also of one’s friends. Real friendship is not only friendship with the people around oneself but also one’s care for the whole society, that is, a kind of justice. Real justice, in turn, not only concerns one’s love for the people and their whole society but also ultimately one’s love for the entire world. Hence, love’s final, full form is one’s devotion to God or religion. Relying on ‘truth’, White thus builds a complete scale of different basic goods – a basic good at a higher level is truer and more ‘complete’ and can drive and transform its secondary basic goods (White 2004 :137–150).

Therefore, White believes that the dependence of an individual basic good on a universal basic good is not an ‘instrumental’ dependence but a logical dependence. An individual basic good is not negated by its universal basic good; rather, it is precisely intensified and fulfilled – an individual basic good can only be fully realised through a more general basic good.

White’s solution can thus be reduced to an analogical structure: self-love is to friendship as friendship is to justice, which, again, is as justice is to devotion to God. By analogy, White asserts God’s love to be the highest and most universal common good.

Undoubtedly, in many texts, Aquinas mentions that charity is the highest and most universal good. Nevertheless, if one looks at Aquinas’ own analysis of the virtues that stem from basic goods, one finds two significant features which conflict with White’s theory and can help reveal Aquinas’ own strategy: firstly, Aquinas does not claim that friendship is the perfect form of self-love nor that justice is the perfect form of friendship; secondly, charity penetrates all basic goods without any medium. The two points are raised, since instead of analogical methodology, Aquinas applies other ontological principles to construct the hierarchy of basic goods, namely the participation and the hylomorphism doctrine and his understanding of human nature. The latter is based on the Aristotelian functional argument and is rejected by Finnis based on the principle of ordering basic goods (McInery 1992 :184–188).

In Summa Theologica, I–II, q. 61, a. 2 (Aquinas 2007 :847), where Aquinas discusses the hierarchical scale of virtues (i.e. the number of primary virtues), his analysis of the four cardinal virtues shows that he constructs his hierarchy of goodness via a de facto method of participation: the highest and perfect goodness is the complete realisation of human nature, that is, prudence. It is followed by its practical application, that is, ‘justice’, which relates to concrete, practical relationships with others (Wright 1907 :156). Moreover, rational restraint (temperance) and promotion of passion (fortitude) follow justice. It therefore follows that friendship and social justice are simply concrete realisations of the virtue of ‘justice’. Accordingly, Aquinas bluntly states that prudence is distinct from the other three, in that it belongs essentially to reason, whereas the other three imply a certain share of reason (participation ratio) through a kind of application of reason to passions or operations (Summa Theologica, I–II, q. 61 a. 4 c., Aquinas 2007 :848).

Additionally, Aquinas (Summa Theologica, I–II, q. 61 a. 4 c., Aquinas 2007 :848) offers another analysis in a hylomorphic way, indicating that these four virtues have their ‘special determinate matter’ (materia specialis) and that reason plays the role of form.

Hence, different virtues are merely habits realised by reason in different parts of human nature – discretionary or theoretical reason, practical reason, operation and passion. The different nobilities of each virtue are not defined by reason itself but by the nobilities that comprise the soul: the intellect is nobler than an active operation, which it leads. An active operation, again, is nobler than a passion. Likewise, the basic goods and their realisations are equally regarded as the ends of reason on different scales of human nature and the proper realisations of these ends (Dell’Olio 2003 :104–105). Thus, each virtue, as well as the respective fundamental good it realises, are equal and irreducible in themselves; they differ only with respect to the nobilities of their subjects.

If one applies the same hylomorphic and participatory framework to analyse the relationship between charity and other virtues, one also finds that like reason, charity pervades all basic goods. One can therefore achieve such infused virtue through any moral practice. Compared with reason, however, charity perfects one at a higher level, since it makes one participate in divine good more directly or closely:

Now, man’s happiness is twofold […] One is proportionate to human nature, a happiness, to wit, which man can obtain by means of his natural principles. The other is a happiness surpassing man’s nature, and which man can obtain by the power of God alone, by a kind of participation of the Godhead […] And because such happiness surpasses the capacity of human nature, man’s natural principles, which enable him to act well according to his capacity, do not suffice to direct man to this same happiness. Hence, it is necessary for man to receive from God some additional principles, whereby he may be directed to supernatural happiness. (Summa Theologica, I–II, q. 62, a. 1 c., Aquinas 2007 :851)

In other words, charity can perfect the intellect and thereby perfects every virtue.

Therefore, as Aquinas states in Summa Theologica I–II, q. 63, a. 4 c., even temperance represents charity:

The object of temperance is a good with respect to the pleasures connected with the concupiscence of touch. The formal aspect of this object is from reason, which fixes the mean in these concupiscences, while the material element is something on the part of the concupiscences. Now, it is evident that the mean that is appointed in such as concupiscences according to the rule of human reason is seen under a different aspect from the mean which is fixed according to Divine rule. For instance, in the consumption of food, the mean fixed by human reason is that food should not harm the health of the body nor hinder the use of reason, whereas according to the Divine rule, it behoves man to ‘chastise his body and bring it into subjection’ (1 Cor 9:27). (Summa Theologica, I–II, q. 63, a. 4 c., Aquinas 2007 :856–857)

Here, a temperate action remains unchanged in terms of its ‘material’, that is, the restraint of passion. However, because of the addition of its connection with God (i.e. charity), its ultimate goal is no longer the happiness of this world (health) but the perfect happiness of the afterlife; it has acquired a transcendent meaning (Dell’Olio 2003 :120–129). A similar example can be found in Summa Theologica I–II, q. 13, a. 1 c., where Aquinas asserts that if one performs an act of fortitude for the love of God, the act is materially an act of fortitude but formally an act of charity (Aquinas 2007 :643). More generally, charity connects all one’s acquired virtue with prudence or reason and transforms the original pursuit of the basic goods in this world to the pursuit of the perfect good in the afterlife, which has God as its ultimate end.

Under such a structure, one finds that whatever God’s love constructs is a higher perfection, an utterly formal principle that is higher than reason or prudence; meanwhile, reason as form determines other virtues. Hence, charity, reason and other virtues build a vertical, hylomorphic hierarchical structure. Meanwhile, the ‘material’, which Aquinas mentions in the citation above, or specific virtues – temperance, fortitude and justice – build a separate horizontal scale, based on the nobility of their respective subjects, that is, the parts of the soul.

Thus, Leo White’s approach may represent a kind of contemporary neo-Thomism, where charity both needs to be accessed through a process of self-love, friendship and justice and is the end of this logical chain, producing a hierarchical order of basic goodness. However, this idea is at a distance from that of Aquinas’ own. The above discussion shows that for Aquinas, charity is a more complete form of wisdom; it leads to a perfect form of human being and to ultimate happiness, the beatific vision, that is, the vision of God (visio Dei) in the afterlife. Therefore, given the above hierarchical sequence of virtues, one can deduce the hierarchical, vertical structure of basic goodness based on hylomorphism or participation: charity (religion) → knowledge → other goods. Meanwhile, there is a distinct horizontal hierarchy based on the respective subjects: knowledge → social life → survival, reproduction, etc.

In conclusion, Grisez’s instrumental exposition of Aquinas’ concept of hierarchical basic goods is clearly justified: according to Aquinas, human virtues ultimately serve the good of the afterlife. However, this instrumental hierarchy implies a fundamental relationship among charity, reason and the other fundamental goods, that is, a relationship of hylomorphism and participation, which is ignored in Grisez’s instrumental interpretation and the following argument: other goods share the highest good – wisdom and its perfect form, charity – and through the latter two, they attain their real fullness. Furthermore, these basic goods form another hierarchical structure based on the nature of their subjects. That the basic goods are commensurable for Aquinas is therefore not because of any analogy like White suggests, but the two named principles. Furthermore, Grisez and Finnis can construct their incommensurability theory of basic goods only by rejecting them as ‘interfering’ with the basic goods order.

In the following section, it is demonstrated how this dual hierarchy can be found not only in Aquinas’ basic goods theory but also in his theory of sin. Discussing Aquinas’ hierarchy of sin can therefore foster a deeper understanding of the hierarchical methodology of his ethics. It also allows one to grasp the ingeniousness and completeness of his moral theory.

Sins and their gravities

In this section, it is first explained what sin meant to Aquinas, followed by a discussion of how Aquinas grades sins on account of their species.

At the beginning of Quaestiones Disputatae De Malo (q. 1, a. 1, c., Aquinas 2003 :59), Aquinas points out that evil (malum) is the lack or privation of a certain good, that is, the lack of something desirable. However, not every privation of good or of being is evil; for example, a lack of wings is not evil by human nature because wings are not a proper good for humans. It should therefore be specified that by evil, the privation of proper reality that is desirable to human nature is meant (Aertsen 1996 :330; Kluxen 1998 :175; Wippel 2016 :22).

Hence, when this evil – the privation of proper realisation – occurs in action, Aquinas calls this ‘peccatum’. Strictly speaking, ‘peccatum’ in Latin should only mean ‘fault’; the absence of good that occurs in one’s actions may be intentional or unintentional, but only an intentional privation should be called ‘sin’ (‘culpa’) (De Malo, q. 2, a. 2, c., Aquinas 2003 :97). Nevertheless, when discussing sin, one is necessarily talking about human action, which involves will and reason (‘actus humanus’), not simply an action of humans (‘actus hominis’). Aquinas therefore often uses the word ‘peccatum’ to refer to ‘sin’ or ‘sinful action’. In short, for Aquinas, sin is an evil that occurs in human action; that is, it is the absence of some proper realisation of human nature, which he signifies with ‘peccatum’ or ‘culpa’.

Now, how does Aquinas measure the gravity of the evil of an action? That is, how does he assign gravity to a sinful action? A brief answer given by Aquinas is as follows: according to the subject of the privation.

To elucidate this, Aquinas (Summa Theologica, I–II, q. 73, a. 3 c., Aquinas 2007 :912) cites disease as an analogy: the gravity of sins varies in the same way as one sickness is graver than another. According to Aquinas, the disease which disorders a more important part of the body by disordering its humours is more severe than other diseases. Similarly, the more fundamental a principle is in the rational order – where the disorder by a sin occurs – the greater is the sin.

In this passage about sins, Aquinas also refers to virtue, saying that ‘the good of virtue consists in a certain commensuration of the human act in accord with the rule of reason’, just as ‘the good of health consists in a certain commensuration of the humours, in keeping with an animal’s nature’. As discussed above, his hierarchical division of the virtues is based on the related subjects. That is, Aquinas assigns the nobility of a basic good according to the nobility of the realisation that this good relates to; the nobler a human perfection a basic good relates to, the nobler this basic good is. Hence, Aquinas’ construction of the hierarchy of sin also starts from the principle of the convertibility of being and goodness, that is, the hierarchy of a sin’s object in terms of its essence. However, because sin is not ‘something’ per se but an absence of something, sins cannot be ranked in terms of their essence, which sinful actions lack, as any action is a certain reality, which necessary achieves a certain good. Thus, there is no action that does not realise any good. How, then, is the hierarchy of evil defined by this ‘essentialism’? Aquinas goes on (Summa Theologica, I–II, q. 73, a. 3 c., Aquinas 2007 :912) to state that one seeks the hierarchy in the object to which an action refers. According to Aquinas’ philosophy of action, the end of an action (finis operis) is the object of the action. Hence, the nobler an object is in the entire order of existence, the more severe the evil act is as a species. That is, as Aquinas states (Summa Theologica. I–II, q. 72, a. 5 c., Aquinas 2007 :906), from the perspective of the offender, the relationship between punishment (signifying the gravity of a sin) and sinful action is outside one’s intention and thus accidental. What kind of good a killer wants to realise has nothing to do with the disorder in society caused by murder. Accordingly, just as God ranks highest in the order of beings (he is not only the highest in terms of perfection but also the cause of all other beings), a human being is higher than other creatures in terms of the perfection of being; he or she is the end or the purpose of all other creatures. Therefore, all external things, the possessions of human beings, rank lower than humans in the order of existence. The hierarchy of the existence of an action’s objects, which are the ends of actions, articulates the gravity scale of the destruction of the proper order of these objects, which corresponds to the hierarchy of the sins. A sin against God, for instance, is higher than a sin against human beings, which is also higher than a sin against other external things.

The process of how Aquinas assigns sins to a hierarchy in terms of their gravity thus underscores how the structure of this discussion is similar to his horizontal hierarchical structure of the basic goods: both hierarchies are based on the nobility of relevant objects. Given that differences in the severity of sins are constructed from an ontological scale, a natural question arises: can a vertical hierarchy also be identified, in terms of hylomorphic perfection – imperfection or participation – concerning sins according to Aquinas’ theory of sins? In the following section, this possibility is explored and validated.

Double structure of the hierarchy of sin

Aquinas distinguishes between radical and nonradical sins, which are venial sins (peccatum veniale) and mortal sins (peccatum mortale), respectively. The difference between venial and mortal sin stems from the diversity of the inordinateness that constitutes the notion of sin (diversitas inordinationis):

For inordinateness is twofold, one that destroys the principle of order, and another which, without destroying the principle of order, implies inordinateness in the things which follow the principle: thus, in an animal’s body, the frame may be so out of order that the vital principle is destroyed; this is the inordinateness of death; while, on the other hand, saving the vital principle, there may be disorder in the bodily humors; and then there is sickness. Now the principle of the entire moral order is the last end, which stands in the same relation to matters of action […]. (Summa Theologica. I–II, q. 72, a.5 c. Aquinas 2007 :906)

An action is, fundamentally, the pursuit of some kind of good. According to the above analysis of Aquinas’ theory of basic goods, the ultimate and highest good that one should seek is God. Therefore, any action (though it also pursues some kind of good) that leads to the impossibility of the realisation of the highest and final end commits the most severe sin. For a form–matter–composed thing, to make it impossible for it to become a good and thus an object of action is to destroy it. For example, by destroying the structure of a table, it becomes unusable and therefore undesirable as such. Nevertheless, how can God, as an immaterial entity that is indestructible, become an undesirable object through a sinful action?

For Aquinas (Summa Theologica. I–II, q. 72, a.5 c. Aquinas 2007 :906), God’s state as a human-desirable object relates to the principle of charity. If one betrays God, one ‘turns away’ (aversion) from God. In this case, the very principle is destroyed, and one can no longer realise one’s final end. In this case, one therefore commits a mortal sin. To illustrate this, Aquinas again uses sickness as an analogy (Summa Theologica. I–II, q. 72, a.5 c. Aquinas 2007):

The mortal illness is the disorder of death, which results from the destruction of the principle of life; it is irreparable according to the nature of our body, while the other illnesses can be cured because of the vital principle being preserved. Therefore, in human action, one who turns away from his last end by sinning is like the mortal, incurable or irreparable illness and therefore is said to sin mortally and deserves eternal punishment. Whereas, when a man sins without turning away from God, this sin is ‘curable’, his disorder can be repaired because the principle of the order is not destroyed; wherefore, he is said to sin venially because he does not sin to deserve an eternal punishment. (p. 906)

Here, it is observed that an action that removes God as the ultimate end of a person’s pursuit is unlike other sins. A mortal sin does not entail destroying an object itself (for this is impossible) but of making one cease to regard God as the final end; that is, it severs the unity of a human being and God.

Furthermore, for Aquinas, the species of an action is determined not only by the object of the action but also by the end of the intention: ‘The species of a human act is considered formally with regard to the [intended] end but materially with regard to the object of the external action’ (Summa Theologica I–II, q. 18, a. 6 c., Aquinas 2007 :667). That is, the intention more fundamentally determines the species of the whole action than the object of the action, which is why Aquinas paraphrases Aristotle – ‘he who steals that he may commit adultery is, strictly speaking, more adulterer than thief’ (Aquinas 2007 :667) – to illustrate this hylomorphic relation: although the object of an action prescribes the species of the action, it is ultimately determined by the intentional end. Accordingly, one can pursue the basic goods on the one hand and deem God the ultimate end and highest good on the other hand. This is also why charity is a perfect form that penetrates all the actions in pursuit of the basic goods. Hence, the same structure can be applied to an analysis of sins: for any venial sin, such as stealing and wounding, even when it does not involve destroying the first principle – that is, turning away from God – per se, as long as its intention entails such disorder, is still a mortal sin. Therefore, Aquinas unsurprisingly states that a venial sin becomes mortal to its agent when he or she directs the action towards an end that is a mortal sin in its own genus (Summa Theologica I–II, q. 18, a. 6 c., Aquinas 2007 :982).

In summary, to explore how Aquinas constructs his hierarchy of sin, one must first examine what ‘sin’ means to Aquinas, for whom a sin is an action that lacks some proper realisation of human nature. Because of its special ontological structure, the hierarchy of sin cannot be established from the hierarchical structure of the good of actions themselves but arises from the ontological status of the objects of an action to which a sin refers. Thus, Aquinas articulates a hierarchy of sin according to the following criteria: blasphemy (concerning God) → harm (concerning human beings) → theft (concerning external things). Next, Aquinas designates forms of ‘radical’ and ‘not radical’ sin based on whether a sin involves the intention of turning away from God, which constitutes a ‘mortal sin’; if this is not the case, the sin is merely a ‘venial sin’.

Thus, one finds that both Aquinas’ hierarchy of basic goods and hierarchy of sin share similarities. On the horizontal dimension, both hierarchies refer to the grades of beings; on the vertical dimension, both hierarchies are constituted by transcendent (God as the final end – severing the connection with God) and nontranscendent (reason–lack of reason) forms or by complete–incomplete forms with their proper materials.

Conclusion

The research until now shows that in Aquinas’ moral theory, the hierarchies of sins and basic goods are isomorphic. It is not an accident: Aquinas uses both the participation-hylomorphic doctrine and the dignity of substance, respectively, to construct the two orders consistently. These ontological principles as a base distinguish his hierarchy model from the model of other modern thinkers like Grisez, Finnis and even White, who do not share the same foundation.

A further point referring to the vertical hierarchies that should be mentioned is that the distinguishing between the perfect and imperfect forms of basic goods (charity and wisdom), as well as between the mortal and the venial sins, is based on Aquinas’ theory of double happiness (beatitudo duplex): the perfect and the imperfect happiness. Aquinas establishes one’s perfect happiness as achieving the ultimate end, God. In this case one must exceed one’s own natural power and with God’s help in the afterlife to fully realise one’s proper nature. This transcendental process implies a new status beyond the connection between one’s reason and body (Speer 2005 :161–163), which relates to the highest basic good, charity. Accordingly, an action leading to the lack of such a realisation is a mortal sin. Meanwhile, the other basic goods relating to wisdom obtain their value from the imperfect happiness in the present life. Similarly, an action that impedes realising this happiness is a venial sin. That is the reason why a dual formal principle is obtained from his hierarchical models.

Acknowledgements

Competing interests

The author declares that they have no financial or personal relationships that may have inappropriately influenced them in writing this article.

Author’s contributions

L.G. is the sole author of this research article.

Ethical considerations

This article followed all ethical standards for research without direct contact with human or animal subjects.

Funding information

The research is supported by the National Social Science Fund of China (ref. no. 21CZX056).

Data availability

Data sharing is not applicable to this article as no new data were created or analysed in this study.

Disclaimer

The views and opinions expressed in this article are those of the author and do not necessarily reflect the official policy or position of any affiliated agency of the author.

References

Aertsen, J., 1996, Medieval philosophy and the transcendentals: The case of Thomas Aquinas, Brill, Leiden.

Aquinas, T., 2003, On evil, transl. R. Regan, Oxford University Press, Oxford.

Aquinas, T., 2007, Summa theologica, 2(2. 1), transl. Fathers of the English Dominican Province, Cosimo, New York, NY.

Dell’Olio, A., 2003, Foundations of moral selfhood: Aquinas on Divine goodness and the connection od the virtues, Peter Lang, New York, NY.

Finnis, J., 2011, Natural law & natural rights, Oxford University Press, Oxford.

Grisez, G. G., 1983, The way of the Lord Jesus: Christian moral principles, Franciscan Press, Chicago, IL.

Kluxen, W., 1998, Philosophische Ethik bei Thomas von Aquin, Felix Meiner Verlag, Hamburg.

Long, S. A., 2001, ‘St. Thomas Aquinas through the analytic looking-glass’, The Thomist: A Speculative Quarterly Review, 65(2), 259–300. https://doi. org/10. 1353/tho. 2001. 0029

McInery, R., 1992, Aquinas on human action: A theory of practice, The Catholic University of America Press, Washington, DC.

Speer, A., 2005, Thomas von Aquin: Die summa theologiae: Werkinterpretationen, Walter de Gruyter, Berlin.

Te Velde, R., 1999, ‘The concept of the good according to Thomas Aquinas’, inW. Goris(ed. ), Die Metaphysik und das Gute. Aufsätze zu ihrem Verhältnis in Antike und Mittelalter: Jan A. Aertsen zu Ehren, pp. 79–104, Peeters, Leuven.

White, A., 2004, ‘Truthfulness, the common good, and the hierarchy of goods’, inJ. Trapani(ed. ), Truth matters: Essays in honor of Jacques Maritain, pp. 137–150, American Maritain Association Publications, Inglewood, CA.

Wippel, J., 2016, ‘Metaphysical themes in De malo I’, inM. V. Dougherty(ed. ), Aquinas’s disputed questions on evil: A critical guide, pp. 12–33, Cambridge University Press, Cambridge.

Wright, H. W., 1907, ‘The classification of the virtues’, The Journal of Philosophy, Psychology and Scientific Methods 4(6), 155–160. https://doi. org/10. 2307/2012190